The invention relates to a toothbrush comprising at least one stationary part, and a brush holder which is adapted to hold a brush and is movable with respect to the stationary part, and a spring which acts between the stationary part and the brush holder, and in which the brush holder can be held in a normal position by the spring force of the spring and in which the brush holder is movable into a deflection position against the spring force of the spring when a given limit value of the cleaning force exerted on the brush during operation of this brush is exceeded.
Such a toothbrush of the type defined in the opening paragraph is known, for example from the document EP 0 636 349 A1, which corresponds to U.S. Pat. No. 5,467,494, issued Nov. 21, 1995. In this known toothbrush the spring arranged between the stationary part and the brush holder is an angled blade spring of which one end portion is straight and fixedly connected to the stationary part and of which the other end portion is bent and cooperates with a stepped pressure surface of the brush holder at the location of the step of this holder. In this known toothbrush the limit value of the cleaning force, above which limit value the brush holder is movable into its deflection position against the spring force of the spring, is mainly determined by a threshold value of the spring force of the angled blade spring and also by the height of the step of the pressure surface and by the frictional conditions between the bent end portion of the blade spring and the pressure surface of the brush holder. However, the threshold value of the spring force depends comparatively strongly on the blade spring tolerances, which basically depend on the thickness of the blade spring, the magnitude of the blade spring angle and the shape of the bent end portion of the blade spring, and the frictional conditions between the bent end portion of the blade spring and the pressure surface of the brush holder are also dependent on tolerances and ageing. Owing to this fact, i.e. the comparatively strong influence of tolerances, the limit value of the cleaning force exerted on the brushes, for which the brush holder moves into its deflection position, exhibits a comparatively wide spread for different samples of the known toothbrush, which is undesirable.